Sponge



FIG. 1 is a perspective view showing the new design for a sponge;

FIG. 2 is a top view thereof, a bottom view being a mirror image thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a left side view thereof; and,

FIG. 5 is a front view thereof, a rear view being a mirror image thereof.

Portions of the drawings shown in broken lines do not form part of the claimed design. 

CLAIM The ornamental design for a sponge, as shown and described. 